Magnetic thread-tensioners



Oct. 30, 1956 P. LEVINE 2,768,796

MAGNETIC THREAD-:TENSIONERS Filed Aug. 12, 1954 INVENTORZ PAUL LEVINE,

WNW

ATTORNEY United States Patent MAGNETIC THREAD-TENSIONERS Paul Levine,Jamaica, N. Y.

Application August 12, 1954, Serial No. 449,426

2 Claims. (Cl. 242-155 This invention relates to thread-tensioningdevices for sewing machines and, more particularly, to athread-tensioning device to maintain a uniform tension of the threadregardless of irregularities in the thread which is wound on a pulley bymeans of a permanent magnet.

A primary object of the invention is therefore to maintain a uniformtension of the thread as it is fed from a pulley to the needle of asewing machine by means of a permanent magnet.

Another object of the invention is to adjust to and maintain a desiredtension of the thread by a permanent magnet which is adjustably mountedon a stud, with the magnetic attraction of the magnet causing a V-shapedgrooved steel pulley on which the thread is wound and which is alsomounted on the stud, to be drawn axially toward the magnet and into atight or loose engagement with a friction plate mounted on the studbetween the magnet and the pulley creating a drag on the pulley andmaintaining a desired tension of the thread as it leaves the pulley.

A further object is to provide a pulley with the sides of the V-shapedgroove at a very small angle so the thread will be wedged into thegroove adjacent its apex and thereby causing the pulley to rotate.

Another object is to provide a pulley with a very small angular grooveso that any lint which may be on the thread will be carried along by thepulley.

A'further object of the invention is to provide a magnetic threadtension unit so that if the thread breaks due to a knot which will notpass through the eye of the needle, the thread is not pulled backthrough the thread guides of the sewing machine.

Another object of the invention is to provide a magnetic thread-tensionunit which is simple in construction and relatively few parts.

These objects and other objects which may appear hereinafter all formpart of this invention.

There is thus provided a magnetic thread-tension unit which may besecured to the head of a sewing machine to provide the proper tension tothe thread as it is fed from a pulley to the need-1e. The unitcomprising a permanent magnet adjustably mounted on a stud along with asmall angular V-shaped grooved steel pulley and a friction plateinterposed between the magnet and the pulley, with the magneticattraction ofthe magnet causing the pulley to be drawn axially towardthe magnet and against the friction plate creating a drag on the pulleyand tensioning the thread which is wound on the pulley. It may thus beseen that the closer the magnet is positioned to the pulley the greaterwill be the magnetic attraction on the pulley and the greater thepressure between the pulley and the friction plate thereby placing agreater tension on the thread as it leaves the pulley.

Referring to the drawings in detail:

Fig. llis a side elevation showing the magnetic thread tension unitattached to a sewing machine head, a frag ment of which is shown;

Fig. 2 is an end view showing the plate of magnetic material which issecured to the north and south poles of the magnet to form a horseshoemagnet;

Fig. 3 is a longitudinal sectional elevational view taken along line 22of Fig. 2 showing the parts of the magnetic tension unit in assembledrelationship;

Fig. 4 is a transverse section taken along line 33 of Fig. 1 showing thenorth and south poles of the magnet mounted in the non-magnetic block;

Fig. 5 is a detail section of the pulley in elevation taken along line4-4 of Fig. 3 showing the manner of winding the thread on the pulley;

Fig. 6 is an exploded view showing the magnetic threadtension unitdisassembled.

Having reference to Fig. 6 a stud of non-magnetic material generallydesignated 10 which is circular in cross section. The stud 10 hasapproximately one-half its length threaded at one end at 11 terminatingin an unthreaded bearing portion 12 and an enlarged diameter unthreadedshoulder portion 13 which terminates in a reduced diameter threaded endportion 14. Rotatably positioned on the unthreaded bearing portion 12 isa steel pulley 15 composed of two halves 16 and 17 respec' tively whichare pressed together to form the assembled pulley. The pulley has anunthreaded bore 13 to permit it to be rotatably positioned over thebearing portion 12. The two halves 16 and 17 thus assembled form a smallangular V-shaped groove G of approximately 8 in which the thread T iswound to be wedged between the side faces 19 and 20 of the grooveclosely adjacent its apex causing the pulley to turn. The two halves 16and 17 also have external side faces 21 and 22 respectively.

Threadably secured on the threaded end 11 of the stud 10 is anon-magnetic face plate or disk 23, preferably of brass, formed with aboss or collar 24. To the outside face 25 of the disk 23 is glued orotherwise secured a cork facing 26 or other friction material which isadapted to frictionally engage the external face 21 of pulley 15.

The face plate or disk 23 has an internally threaded bore 27 with thethreads of the bore engaging the threads 28 of the threaded end 11 whenthe disk is positioned on the stud 10. The disk 23 is rotated until thethreaded bore 27 engages the last thread 28 of the threaded end 11 sothe cork facing 26 may frictionally engage the external face 21 of thepulley 15.

A permanent magnet designated M comprises magnetic poles north and southwhich are held within a solid centrally bored block B of any suitablenon-magnetic material, preferably brass, with the poles connected attheir outside ends by a plate P of magnetic material having a centralbore 29, and the plate being secured to the poles by means of screws 30thus forming a horseshoe magnet.

The block B has a central threaded bore 31 at one end and which isenlarged and unthreaded at the other end forming a recess 32 for theboss or collar 24 of the disk 23.

tioned on the stud to prevent axial movement outwardly of the magnet.

In Fig. 5 there is shown the thread T wound around the pulley G as itcomes from the feeding spool, not

shown, on the sewing machine, and T shows the thread was it leaves thepulley to pass through a hook or guide, 3

3 not shown, mounted upon the sewing. machine head H and thence to theneedle. It may thus be seen that the thread T leaves the pulley 15- at atangent permitting the thread to slip out of the groove G easily andtherefore not bind.

In operation and with the parts assembled as best shown in Fig. 3 thethread T'is. pulled through:v the machine by the action of the stitchesbeing formed and fed away from the needle. Since a sewingmachine mustoperate with a very light thread tension in order to prevent puckeringof the stitches, the conventional 60 or U-shaped grooved pulleys are notsuitablebecause the untensioned thread will slip over the pulley ratherthan revolve it. To place the maximum but comparatively light tensionon. the thread. T it.may' bev seen from the figure that the magnet Mwill exert-its" greatest magnetic attraction to pull the pulley 15axially toward the magnet and against the cork facing 26 of the faceplate or disk 23- when the magnet is positioned in abutting:relationship with the plate 23 thus creating amaximum drag on the pulley15 and placing the thread T under a steady but light tension.

If it is desired to obtain a lighter tension on the thread T the nut 33.is loosened releasing the lock washer 34- permitting the magnet M to bemoved axially along the threaded end 11' of the stud 10 and away fromthe disk- 23 any desired distance thus decreasing the magneticattraction. between the pulley 15 and the magnet M and therebydecreasing the frictional contact between the cork facing 26 and theexternal face 21 of the pulley. The

tension of the thread T may thus be varied anyamount larities in thethread or different diameterthreads willhave no eifect on the formationof the stitch. Anylint which may be on the thread T will be carriedalong in-- stead of getting caught between the pulley as new happensbetween the pressure washers of the conventional tension devices where.accumulated lint forces the washers open and causes the tension to bereleased.

Since the thread tension unit is not of the hysteresis type, if thethread T breaks due to a knot which will not pass through the eye of theneedle, the thread is not pulled back through the guides of the sewingmachine as occurs when the thread breaks in the hysteresis type oftension device. It is only necessary to-rethread the needle and not theguides, thereby saving the operator considerable time.

As this invention may be embodied in several forms without departingfrom the spirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all changes that fall within themetes and bounds of the claims or that formtheir functional as well asconjointly cooperative equivalents, are therefore intended to beembraced by those claims.

What is claimed is:

1. A thread-tensioning device for sewing machines comprising a stud ofnon-magneticmaterial' having at one end an end portion of a shape forsecuring to a sewing machine, said stud having a threaded part extendinginwardly from its other end and having an unthreaded bearing portionadjacent the inner end of said' threaded part with an enlarged diameterportion inwardly of said unthreaded portion forming a shoulder at theinner end thereof, a solid cylindrical block of non-magnetic materialhaving a central longitudinally extending threaded bore in adjustablethreaded engagementwith said threaded part of the stud providing forlongitudinal adjustment of said block on the stud, a permanent magnetmounted on said block, a circular plate of non-magnetic material havinga central hub part fixed on the stud at the outer end of said unthreadedbearing portion of the stud at the inner side of said block, and saidplate having a friction facing on the inner side face thereof, a smallV- shaped grooved pulley of magnetic material mounted for rotation andfree axial movement onsaid unthreaded bearing portion of the stud, thepulley having side wall portions fixed with relation to each other andthe central part of the pulley, and a lock nut on the threaded part ofthe stud for holding said block with the magnet thereon in differentpositions of adjustment on the stud, said magnet through its magneticattraction on the pulley causing the pulley to be moved axially to bringone of its side faces against the friction facing of said plate andthereby effect adrag on the pulley and tensioning of the thread.

2; A thread-tensioning device for sewing machines comprising a stud ofnon-magnetic material having at one end an end portion of a shape forsecuring to a sewing machine, said stud having a threaded part extendinginwardly from its opposite end and having an unthreaded portion adjacentthe inner end of said threaded part with an enlarged diameter portioninwardly of'said unthreaded portion forming a stop shoulder at the innerend thereof,. a solid cylindrical block of non-magnetic material havinga central longitudinally extending threaded bore in threadedengagementwith' said threaded part. of the stud providing forlongitudinal adjustment of said block on the stud; and said block havingapair of longitudinal bores extending from end to end thereof atdiametrically opposite locations outwardly of the central bore, a horseshoe magnet comprising elongated north and south pole elementsheld insaid pair of bores in the block and each extending from end to end' ofthe block and having a threaded aperture in its outer end, a

connector plate of magnetic material fitting against the outer ends ofsaid pole elements and the block, said connector plate having a centralaperture to accommodate the outer end of said unthreaded bearing portionof the stud at the inner side of said block, and said'plate' having afriction facing on the inner side face thereof, a small V-shaped groovedpulley of magnetic material mounted for rotation and free axial movementon said'unthreaded bearing portion of the stud, the pulley having sidewall portions fixed with relation to each other and the central part ofthe pulley, and a lock nut on the threaded part of the stud for holdingsaid block with the magnet thereon in different positions of adjustmenton the stud, said magnet through its magnetic attraction on the pulleycausing the pulley to be moved axially to bring one of its side facesagainst the fraction facing of said plate and thereby effect a drag onthe pulley and tensioning of the thread.

References Cited in the file of this patent UNITED STATES PATENTS 22,045Wheeler Nov. 9, 1858 751,930 Lundgren Feb. 9, 1904 2,073,818 Viens Mar.16, 1937 2,361,239 Ransom Oct. 24, 1944 2,605,301 Barnes July 29, 19522,614,773 Ammerall Oct. 21, 1952 2,650,043 Grein Aug. 25, 1953 2,724,065Saxl Nov. 15, 1955 FOREIGN PATENTS 864,717 France Jan. 27-, 1941

